The story of a good deed has spread like wildfire online since Sunday, when an anonymous do-gooder left a kind note and $40 on a woman’s windshield in a Dunkin’ Donuts parking lot.

“I noticed the sticker on the back of your car,” the note read, referring to a “Half my Heart is in Afghanistan” bumper sticker. “Take your hero out to dinner when he comes home. Thank you both for serving. Him deployed and you for waiting.” It was signed “United States veteran” and “God Bless.”

The woman, Samantha Ford, a mother of two who lives outside of Boston, quickly snapped a photo of the note and the cash, and shared it on the Facebook page “Our Deployment: 101,” a sort of online support community for people affiliated with the military.

“I just thought I would share with you all what happened to me today!” Ford wrote when she posted the photo. “Came out of Dunkin’ Donuts and found this under my windshield wiper. There are no words to describe how I'm feeling right now. Tears in my eyes. I just wish I could thank whoever did this! God bless our troops and all of those who stand behind them.”

By Tuesday morning, the post had a million and a half “likes,” had inspired more than 43,000 comments, and had been shared nearly 200,000 times.

“It was crazy!!” Ford said in an email to TODAY.com, adding that she’d spoken to her boyfriend Sunday night and told him about the gesture. “He was so touched, and he said it’s people like this that make him proud to be an American Soldier. We are forever grateful and we will DEFINITELY be paying it forward! God bless our troops!”